ENTRAINED GAS IN LUBRICATION OIL

BioKem Oil Services has specialist equipment that will remove 100% of entrained gas from lubricating and hydraulic oil.

BioKem has the equipment and the know-how to perform on-site oil filtration, dehydration and removal of entrained gases from your lubrication oil.  Entrained gas is not just problematic from simple air bubble generation, but can also ‘dilute’ or lower the mineral oil viscosity of the oil.

Is the presence of entrained gases affecting your lubrication circuit?

If the lubricating oil comes into contact with gas at an elevated temperature and pressure then gas entrainment may occur.  ‘Entrainment’ or ‘fluid aeration’ can cause numerous problems in hydraulic and lubrication oil systems including: unacceptable noise, poor component response due to spongy behaviour of aerated fluids, cavitation damage and severe fluid degradation.  If bubbles are present in the fluid in the reservoir, they may be sucked into the pump, where the bubbles’ volume will increase, due to pressure decrease along the suction line, and then compress again when a region of higher pressure is encountered. This compression is nearly adiabatic (the bubble gets hot, but does not materially increase the temperature of the surrounding fluid), resulting in tremendous localized temperatures at the gas-liquid interface. This may cause thermal cracking and sludge/varnish formation. In compressors, various process gasses, including soluble hydrocarbons like methane, butane, propane, petro-chemical processing sour gases, etc., are soluble in mineral oils and effectively cause ‘dilution’ or a lowering of the mineral oil viscosity reducing lubricant efficacy.

Cambridge Viscosity President Robert Kasameyer says that "when the compressor is running, the lubrication oil is hot and the entrained gas remains in gaseous phase. When the compressor is down, the lubrication oil cools and some of this gas can become liquid, which causes the lube oil viscosity to drop. Then, when the equipment is re-started but before it heats up, the equipment is operating with inadequate lubrication, which can be a disaster! If it makes it through this stage, the light hydrocarbons will again become gaseous, separating out of the lube oil, and the lube oil will regain its proper viscosity. But the damage will already be done."

The key thing to know is that once oil has been absorbed into the gas flow, it will not be collected by the oil separator.

Bubble removal devices can be used to mechanically remove bubbles from fluids however this is not a 100% effective method and foaming can occur.  Removal of entrained gas with a vacuum dehydrator provides for 100% removal of entrained gases and advantages such as the possibility of smaller reservoir size and lower overall system cost. 

BioKem VDOPS achieving ISO 10/8/7

The installation of an in-service, kidney loop, BioKem Oil Services vacuum dehydrator (VDOPS) will ensure that 100% of entrained gas and 90% of dissolved gas is removed and that the oil is free from not only gas, but is very dry and clean.  Our VDOPS systems are equipped with high efficiency pleated Microglass filter elements rated Beta(c)1000 per ISO 16889 to quickly and reliably achieve very low particle counts to meet or exceed an ISO 16/14/11 cleanliness level.

BioKem VDOPS 190l/min vacuum dehydrator

SGSpost filter Lab Test of 5,000l lube oil tank showing a moisture level of 8ppm!

Clean Lube Oil Increases the Life of Rotational Equipment

Lubrication oil cleanliness is probably the single most important factor determining your rotational equipment longevity.

The British Hydromechanics Research Association (BHRA) conducted a three year controlled “field” study of 117 hydraulic machines.  The field trial was established with the sole purpose of correlating fluid cleanliness to breakdown frequency.  The results published are extremely compelling and worthwhile heeding.

You would assume that operating machinery within oil cleanliness specifications should assure that the life of the equipment is reasonable, R&M is fair and downtime minimised.  But what if the lube circuit oil is maintained at several levels of cleanliness above the norm?  The answer is surprising and the BHRA study shows that based on a datum of ISO 18/15 oil that oil that is two grades ‘cleaner’ will outperform the datum oil by 1.8x reliability based on breakdowns.  If the oil is running dirtier at ISO 22/19 then breakdowns are far more frequent and more than twice as problematic.

The chart also shows that the new ‘clean’ oil received from a supplier is typically ISO 21/18, and potentially harmful to your machinery if not polished before first use. 

If you suffer an event that compromises the cleanliness of your oil contact BioKem and seek advice as the oil can be recovered, dehydrated, filtered and polished so that it exceeds a new oil spec … a cheaper and possibly quicker solution than ordering new oil.

Research

In the 1990’s Nippon Steel implemented a hydraulic system contamination control program plant-wide, involving both improved filtration and rigorous fluid cleanliness monitoring, and pump replacement frequencies were reduced to one fifth and the cumulative frequency of all tribological failures (i.e., failures relating to wear and contamination) were reduced to one tenth.

Kawasaki Steel also implemented a similar oil contamination control program and almost achieved a 97% reduction in hydraulic component failures. Such claims as these spurred the British Hydromechanics Research Association (BHRA) and the U.S. Navy to conduct their own controlled studies to substantiate benefits of proactive contamination.

The BHRA study covered a three-year period and was based on the carefully monitored field experience of 117 hydraulic machines across various categories (i.e., injection moulding, machine tools, material handling, mobile/construction, marine, metal working, test stands, and miscellaneous). The results of the study showed a dramatic relationship between fluid contamination levels and service life.  Improved system cleanliness achieved extended actual mean time between failures (MTBF) from 10 to 50 times, depending on cleanliness.  A study by the Naval Air Development Centre in Warminster, Pennsylvania performed on aircraft hydraulic pumps showed nearly a 4-fold wear-life extension with a 66 percent improvement in filtration and a 13-fold wear-life extension with a 93 percent improvement in filtration. Solution

BioKem has the equipment to perform on-site oil purification to rectify post-event lubrication circuit contamination without discarding the oil and installation of conditioning vacuum dehydration equipment running kidney loop filtration.  BioKem can also presecribe and supply static solutions to resolve chronic oil cleanliness concerns.  Should you require a professional service to filter or HOF your circuitry, spools, coolers, lube tanks, manifolds then contact BioKem Oil Services.

www.biokem.com.au

Hot Oil Flushing Methodology

What is Hot Oil Flushing?

Hot Oil Flushing (HOF) is designed to remove contaminants from the manufacturing process/transportation/site assembly, or a contamination event during operation, of a lube oil circuit, by flushing hot oil through the circuit at a minimum of 150% of its operational flow rate, achieving a minimum of Reynolds 4000 number, a unit of measure for turbulent flow. The theory being that contaminants such as pipe scale, welding slag and particles, are removed at 150% of operational flow and won’t contaminate the system at operational flow rate.

So what is the purpose of Hot Oil Flushing?

1. We HOF for several reasons,
2. New asset pre-commissioning,
3. Lubricant type change,
4. After a contamination event,
5. Scheduled maintenance

All OEM plant and equipment suppliers have their own methodology and specifications for pre-commissioning or hot oil flushing their assets.

Most conform to the two established standards ASTM D6439, and API 614.  The Standards require you to capture bulk particles on the return circuit via a screen or filtration, to prevent tank contamination, as you will require this oil to achieve a cleanliness specification prior to start up.

BioKem Oil Services works with both ASTM D6439 and API 614. Standards. WE believe it’s quite advantageous to capture all bulk particles and contaminants in the return circuit, to keep the lubricant within its ISO 4406 or NAS Class specification.

Also advantageous, is to apply fine filtration and vacuum dehydration, via kidney loop to the lube tank, not only are you removing contaminants and particles from the circuitry, but also purifying the oil to a minimum ISO 4406 code of 16/14/12 (NAS Class 6), and moisture content to below 200 ppm.

Service Oil or Base Flushing Oil?

Depending on the application, a service oil or a base oil similar to the final service oil can be used to flush the circuitry.  This decision is based on the availability of service oil, volume of oil needed for the flush, and the timings between flushing and equipment entering service.  In some circumstances the equipment circuits/spools may not enter service for some time afterwards and the final selection of service oil may not have been made or awarded.  In this circumstance a base oil can be used and then the pipework blown dry with compressed air and a purge of nitrogen or similar gas used.  If service oil is used then the HOF team will need to polish (fine filter) the oil ready for service.

Purging the system

If the circuitry can be sealed at the conclusion of the flushing then nitrogen (or other inert gas) can be used to stave off corrosion.  The methodology is to purge all oxygen from the circuits by venting the system whilst it is filled with inert gas.   Correct safety protocols should be followed as Nitrogen can be dangerous in confined spaces.

What Next?

Should you require a professional service to HOF your circuitry, spools, coolers, lube tanks, manifolds then contact BioKem Oil Services www.biokem.com.au